Method for Forming an End Part of a Tube, Respective Device for Performing the Method, Rolling Body, and Flange on an End Part of a Tube Formed with the Method

Abstract

A method for forming an end part of a tube, such as a hollow shaft for use as a vehicle axle, is described. A rolling body having a rolling surface with an inwardly-curved contour rotates around a longitudinal axis with a first rotational speed and a second rotational speed. The rolling body and the tube rotate in the same direction. The longitudinal axis of the rolling body is arranged eccentrically to a longitudinal axis of the tube by a predetermined normal distance. The rolling body and the tube are brought into contact such that the rolling surface contacts the end part of the tube at a contact surface situated on an inner tube wall. The rolling body transfers a force to the inner tube wall by a relative movement between the rolling body and the tube such that the end part of the tube is formed radially outward.

1 . A method for forming an end part of a tube, preferably of a hollow shaft suitable for use in a vehicle, especially a hollow axle shaft, wherein:
 a rolling body rotates around its longitudinal axis with a first rotational speed,   wherein the rolling body is substantially cone shaped or truncated shaped,   wherein the rolling body has a rotationally symmetrical rolling surface around its longitudinal axis, and   wherein the contour of the rolling surface is at least sectionally curved inward,   the tube rotates around its longitudinal axis with a second rotational speed,   the rolling body and the tube rotate in the same direction,   the longitudinal axis of the rolling body is arranged parallel to the longitudinal axis of the tube,   the longitudinal axis of the rolling body is arranged eccentrically to the longitudinal axis of the tube by a predetermined normal distance,   the rolling body and the tube are brought into contact such that the rolling surface of the rolling body contacts the tube in the end part region of the tube at a contact surface situated on an inner tube wall,   wherein the first rotational speed and the second rotational speed are set such that the absolute value of the difference calculated from a circumferential speed of the rolling body minus a circumferential speed of the tube at the contact surface in relation to the circumferential speed of the rolling body is in the range of 0 to 10%, preferably 0 to 5%, more preferably 0 to 2%, and   wherein the rolling body transmits a force to the inner tube wall of the tube in the region of the contact surface by a relative movement between the rolling body and the tube such that the end part of the tube is formed radially outward.   
     
     
         2 . The method according to  claim 1 , characterized in that the force is not more than 500 kN, preferably in a range between 1 and 400 kN, preferably in a range between 5 and 300 kN, more preferably in a range between 10 and 250 kN. 
     
     
         3 . The method according to  claim 1 , wherein when a projection of the contact surface and a projection of the rolling surface are on a plane perpendicular to the longitudinal axis of the rolling body, the projection of the contact surface is entirely enclosed in a circle sector of the projection of the rolling surface, and
 wherein the circle sector comprises an angle at center of not more than 240°, preferably of not more than 180°, preferably of not more than 150°, more preferably of not more than 120°.   
     
     
         4 . The method according to  claim 1 , wherein the material of the end part of the tube abuts on an inner side of a circumferential collar on an outer circumference of the rolling body over a period of time during the forming from a first contact with the inner side. 
     
     
         5 . The method according to  claim 1 , wherein the first rotational speed of the rolling body is between 300 to 1500 rpm, preferably between 450 to 1100 rpm, more preferably between 600 to 700 rpm. 
     
     
         6 . The method according to  claim 1 , wherein the second rotational speed of the tube is between 300 to 1500 rpm, preferably between 450 to 1100 rpm, more preferably between 600 to 700 rpm. 
     
     
         7 . The method according to  claim 1 , wherein the end part of the tube has a temperature between 700 to 1300° C., preferably between 1000 to 1250° C., more preferably between 1150 to 1200° C., at least during a time when the rolling body is in contact with an inner wall of the end part of the tube. 
     
     
         8 . The method according to  claim 1 , wherein the rolling body has a temperature between 100 to 250° C., preferably between 140 to 210° C., more preferably between 150 to 200° C., at least during a time when the rolling body is in contact with an inner wall of the end part of the tube. 
     
     
         9 . The method according to  claim 1 , wherein the tube is warm-upsetted before being formed by means of the rolling body. 
     
     
         10 . The method according to  claim 1 , wherein after the forming by means of the rolling body, the upsetted end part of the tube is further formed by means of at least one pressure forming process. 
     
     
         11 . A flange on an end part of a tube, preferably of a hollow shaft suitable for use in a vehicle, especially a hollow axle shaft, manufactured using the method according to  claim 1 . 
     
     
         12 . The flange according to  claim 11 , wherein a ratio between an outer diameter of the formed end part of the tube to an outer diameter of a not formed portion of the tube exceeds 1.5:1, preferably exceeds 2:1, preferably exceeds 3:1, and more preferably exceeds 4:1. 
     
     
         13 . The flange according to  claim 11 , wherein the formed end part of the tube has at least one portion with a wall thickness which is greater than a wall thickness of a not formed portion of the tube. 
     
     
         14 . A device for forming an end part of a tube, preferably of a hollow shaft suitable for use in a vehicle, especially a hollow axle shaft, preferably suitable for performing the method according to  claim 1 , wherein the device comprises:
 a rolling body with a longitudinal axis, wherein the rolling body is substantially cone shaped or truncated shaped, wherein the rolling body has a rotationally symmetrical rolling surface around its longitudinal axis, and wherein the contour of the rolling surface is at least sectionally curved inward; and   a rotatable means for receiving and attaching the tube, wherein the longitudinal axis of the rolling body is arranged eccentrically to a longitudinal axis of the tube by a predetermined normal distance, and parallel to the longitudinal axis of the tube, when the tube is attached to the means.   
     
     
         15 . The device according to  claim 14 , wherein the ratio of the normal distance to an outer diameter of the end part of the tube before said forming is in a range of 1:60 to 1:2, preferably 1:30 to 1:3, and more preferably 1:6 to 1:3. 
     
     
         16 . The device according to  claim 14 , wherein the rolling body can be driven axially around its longitudinal axis, preferably by means of a drive shaft. 
     
     
         17 . A rolling body for forming an end part of a tube, preferably of a hollow shaft suitable for use in a vehicle, especially a hollow axle shaft, preferably suitable for performing the method according to  claim 1 ,
 wherein the rolling body is substantially cone shaped or truncated shaped,   wherein the rolling body has a rotationally symmetrical rolling surface around its longitudinal axis,   wherein the contour of the rolling surface is at least sectionally curved inward,   wherein a circumferential collar is arranged at an outer circumference of the rolling body, and   wherein the collar has a draft angle larger than 0°, preferably larger than 1°, and more preferably larger than 5°.   
     
     
         18 . The rolling body according to  claim 17 , wherein a tangent to a radially outward edge portion of the rolling surface and the longitudinal axis define an angle larger than 70 to 105°, preferably larger than 75 to 100°, and more preferably larger than 80 to 95°.